Method of manufacturing a semiconductor device

ABSTRACT

Exuding of a interconnecting material to a substrate, which occurs because of a thinned state of and a beak in a barrier metal layer is prevented, irrespective of a laminated state of the barrier metal layer. In the present invention, a protective layer is formed on a side wall by using an insulating film or the like after the deposition of the barrier metal layer, whereby the interconnecting material can be prevented from exuding to the substrate due to influence of heat treatment such as alloying, irrespective of the laminated state of the side wall of the contact hole and the barrier metal layer. Further, the formation of the protective layer allows the side wall to be smoother to thereby improve coverage of the interconnecting material at the same time.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacturing asemiconductor device.

2. Description of the Related Art

Recent progress in high integration of semiconductor devices has make itgeneral to utilize multi-layered interconnect in the semiconductordevices. In addition, interconnects and connection holes (contact holesand via holes) are increasingly downsized along with miniaturization ofthe semiconductor devices, making it more difficult to sufficientlyfulfill interconnecting material into the connection holes. Insufficientfilling of connection holes causes bad effects such as a break ininterconnection and occurrence of a contact pit. Hence, a conductivebarrier metal layer is formed before deposition of an interconnectingmaterial such as Al—Si or Al—Si—Cu. The barrier metal layer is generallyformed by depositing Ti or both Ti and TiN by chemical vapor deposition(CVD). Because Ti has better heat resistance and auto-flatness than Aland the like described above, Ti is effective in eliminating thenegative effects described above.

The procedure for manufacturing interconnection and connection holes ina conventional semiconductor device is described with reference to FIGS.2A to 2D.

A first interlayer insulating film 102 and a second interlayerinsulating film 101 are formed on a semiconductor substrate 103 bychemical vapor deposition (CVD). A TEOS, a silicon oxide film (BPSGfilm) including boron and phosphorus, or the like is used for theseinterlayer insulating films (FIG. 2A).

Next, a contact hole is formed in these interlayer insulating films.Herein, a method of improving coverage of an interconnecting material isdescribed from among several methods of forming a contact hole. First, aresist film 107 is used as a mask and isotropic etching is performed upto a certain depth to expand an opening of a contact hole, and thenanisotropic etching is performed to form the contact hole (FIG. 2B).

Subsequently, a barrier metal layer 104 is formed in the connectionhole, and an interconnecting material 106 is deposited thereon. Further,a mask pattern is formed on the interconnecting material 106 by aphotolithography process to form an interconnect pattern by etching(FIGS. 2C and 2D). (See, for example, JP08-330252 A.)

Problem to be Solved

However, in a case where the barrier metal layer is formed by the methoddescribed above, a break in the barrier metal layer may occur. Since theinterlayer insulating films including different materials such as TEOSand BPSG are deposited, etch rates are different and hence it isdifficult to form an even and smooth side wall. When the side wall ofthe contact hole is not smooth, uniform deposition of the barrier metallayer becomes difficult to attain, due to, for example, a local thinningof the barrier metal. In addition, the interlayer insulating films arethermally expanded due to influence of heat treatment such as alloyingafter the deposition of the interconnecting material. As a result,irregularities of the side wall become more remarkable, and a break inthe barrier metal layer may occur. When the barrier metal layer breaksor the thickness thereof locally becomes thin, a spiking phenomenonoccurs in which silicon exudes from Al—Si—Cu or Al—Si, which is theinterconnecting material for an upper layer of the barrier metal layer,to the semiconductor substrate via the barrier metal layer, and theninterconnect deterioration and local increase of current (leakage)occur.

FIG. 3 shows a remarkable defect. Presence of an oxide film 108 which isliable to be corroded by etching leads to formation of a reverse taperedstructure at the interface between the oxide film 108 and the firstinterlayer insulating film 102. Since manufacturing process of asemiconductor is complicated, in which a plurality of insulating filmsare laminated, there exists a portion which is liable to break or becomethin shown as a portion A.

An improved method of providing a side wall in a contact hole isproposed in JP 08-330252 A against the defect described above.

SUMMARY OF THE INVENTION

According to the present invention, there is proposed a method ofmanufacturing a semiconductor device having a structure in which a breakin interconnection can be prevented and a structure in which exuding ofthe interconnecting material is prevented and generation of a defect ishindered.

In order to solve the above-mentioned problem, the present inventionemploys the following method of manufacturing.

The present invention provides a method of manufacturing a semiconductordevice, in which a contact hole and interconnects are formed, the methodincluding: forming a first insulating film and a second insulating filmon a semiconductor substrate; forming the contact hole connecting thesemiconductor substrate and the interconnect formed on the firstinsulating film and the second insulating film; depositing a barriermetal layer thereon and then depositing a protective layer for givingprotection against exuding of an interconnecting material to thesemiconductor substrate to etch an unnecessary portion; depositing theinterconnecting material thereon; and forming a interconnect maskpattern by a photolithography technology and forming an interconnectpattern by etching.

In the present invention, another interconnect layer is further formedabove the first interconnect layer. A plurality of interconnect layersmay be formed on the first interconnect layer. Further, as to thelamination of the insulating film such as the second insulating film, amaterial thereof and the number of layers is appropriately selected, andthe configuration thereof is not limited.

Benefit of the Invention

Through the formation of the protective layer made of an insulating filmon the side wall after the deposition of the barrier metal layer, theinterconnecting material can be prevented from exuding to thesemiconductor substrate due to the influence of the heat treatment suchas alloying, irrespective of the laminated state of the side wall of thecontact hole and the barrier metal layer. Besides, through the formationof the protective layer, the side wall can be made smoother, and hencethe coverage of the interconnecting material can be improved at the sametime. Further, isotropic etching is performed on the protective layer.Accordingly, a photomask or a photolithography process needs not to beadded particularly for etching of the protective layer. Only depositionand etching processes for the protective layer need to be added.

Further, the protective layer is formed on the barrier metal layer, andhence the interconnecting material can be prevented from exuding to thesemiconductor substrate due to the influence of the heat treatment suchas alloying, irrespective of lamination variation in barrier metallayer.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a schematic sectional view showing an example of asemiconductor device manufactured by a method of manufacturing asemiconductor device according to the present invention;

FIGS. 2A to 2D are schematic sectional views in a process order, showinga method of manufacturing a conventional semiconductor device;

FIG. 3 is a schematic sectional view showing a defect in theconventional semiconductor device; and

FIGS. 4A to 4F are schematic sectional views in a process order, showinga method of manufacturing a semiconductor device according to anembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A method of implementing the present invention is described withreference to FIGS. 1 and 4A to 4F.

Hereinafter, a first embodiment of the present invention is described.

First, a silicon oxide film serving as a first interlayer insulatingfilm 102 is formed on a semiconductor substrate 103 by CVD. Further, asecond interlayer insulating film 101 such as a BPSG film is depositedon the silicon oxide film (FIG. 4A). A resist film 107 is formed on thesecond interlayer insulating film 101, and a photomask is formed by aphotolithography technology.

Next, isotropic etching is performed up to a certain depth to expand anopening of a contact hole, and then anisotropic etching is performed toform the contact hole (FIG. 4B). Besides, there is a method ofperforming heat treatment to round corners of the opening of the contacthole. Though those methods, a break in the interconnecting material andcoverage can be improved.

Then, a barrier metal layer 104 is formed on an inner wall of thecontact hole. Ti or both Ti and TiN are used for the barrier metal layer104 in many cases. Ti or both Ti and TiN are formed on the element bysputtering (FIG. 4C).

In the sputtering process, when the side wall of the contact hole is notsmooth, the thickness of the barrier metal layer locally reduces or thebarrier metal breaks, whereby the silicon within the interconnectingmaterial of the upper layer exudes in the semiconductor substrate. Inorder to dissolve this exuding, a protective layer 105 made of aninsulating film is deposited after the deposition of the barrier metallayer by sputtering (FIG. 4D). A BPSD film or an NSG film may be used asthe protective layer. Subsequently, the protective layer 105 ispartially removed by anisotropic etching. Through anisotropic etching,the insulating film can be left, without using a photomask, on a surfaceof the barrier metal layer formed on the side wall of the contact hole,and on a surface of the barrier metal layer formed on a side bottomsurface, which corresponds to a junction between the side wall of thecontact hole and a bottom surface thereof (FIG. 4E). With thisstructure, the surface of the barrier metal layer inside the contacthole is made smooth to thereby produce an effect of improving thecoverage of a interconnecting material which is formed thereafter.

Next, an interconnecting material 106 such as Al—Si or Al—Si—Cu isdeposited by sputtering. Though not shown in the figures particularly, aresist film is applied on the interconnecting material to form a maskpattern, and then an interconnect pattern is formed by etching (FIGS. 1and 4F).

Hereinafter, a second embodiment of the present invention is described.

In the first embodiment of the present invention described above, in acase where a thin film which is easier to be etched than the firstinterlayer insulating film exists between the semiconductor substrateand the first interlayer insulating film, there is a portion in whichthe thickness of the barrier metal layer is locally reduced as shown inFIG. 3. The protective film is deposited thereon. Then, throughanisotropic etching, the insulating film can be left on the surface ofthe barrier metal layer formed on the side wall of the contact hole, andon the surface of the barrier metal layer formed on the side bottomsurface, which corresponds to a junction between the side wall of thecontact hole and the bottom surface thereof. With this structure, thesurface of the barrier metal layer inside the contact hole is madesmooth to thereby produce an effect of improving the coverage of ainterconnecting material which is formed thereafter.

1. A method of manufacturing a semiconductor device, comprising: forminga first interlayer insulating film on a surface of a semiconductorsubstrate; forming a second interlayer insulating film on a surface ofthe first interlayer insulating film; performing patterning on a resistfilm applied on a surface of the second interlayer insulating film;etching the first interlayer insulating film and the second interlayerinsulating film by using the resist film as a mask to form an opening upto the surface of the semiconductor substrate; forming a barrier metallayer on an inner wall of the opening and on the surface of the secondinterlayer insulating film; depositing a protective film made of aninsulating film on a surface of the barrier metal layer; performing anisotropic etching to the protective film to leave the insulating filmhaving a side wall shape so as to cover the surface of the barrier metallayer formed on a side wall of the opening, and the surface of thebarrier metal layer formed on a side bottom surface of a contact hole,which corresponds to a junction between a side wall of the contact holeand a bottom surface of the contact hole; depositing an interconnectingmaterial on the insulating film of the side wall shape, the barriermetal layer, and the surface of the second interlayer insulating film;and etching the barrier metal and the interconnecting material into adesired shape.
 2. A method of manufacturing a semiconductor device,comprising: forming a first interlayer insulating film on a surface of asemiconductor substrate; forming a thin film easier to be etched thanthe first interlayer insulating film between the semiconductor substrateand the first interlayer insulating film; forming a second interlayerinsulating film on a surface of the first interlayer insulating film;performing patterning on a resist film applied on a surface of thesecond interlayer insulating film; etching the first interlayerinsulating film and the second interlayer insulating film by using theresist film as a mask to form an opening up to the surface of thesemiconductor substrate; forming a barrier metal layer on an inner wallof the opening and on the surface of the second interlayer insulatingfilm; depositing a protective film made of an insulating film on asurface of the barrier metal layer; performing anisotropic etching onthe protective film to leave the insulating film in a side wall shape soas to cover the surface of the barrier metal layer formed on a side wallof the opening, and the surface of the barrier metal layer formed on aside bottom surface of a contact hole, which corresponds to a junctionbetween a side wall of the contact hole and a bottom surface of thecontact hole; depositing a interconnecting material on the insulatingfilm in the side wall shape, the barrier metal layer, and the surface ofthe second interlayer insulating film; and etching the barrier metal andthe interconnecting material into a desired shape.
 3. A method ofmanufacturing a semiconductor device according to claim 1, wherein: theprotective film comprises one of a BPSG film and an NSG film; and thebarrier metal layer comprises one of a TiN and a two-layered filmincluding Ti and TiN.
 4. A method of manufacturing a semiconductordevice according to claim 2, wherein: the protective film comprises oneof a BPSG film and an NSG film; and the barrier metal layer comprisesone of a TiN and a two-layered film including Ti and TiN.